The invention pertains to a technique for measuring one or more structural parameters or mechanical properties of polymeric fibres, or for determining their dye uptake.
When spinning polymeric fibres from a polymeric melt or from a solution, the melt or solution is extruded through a spinneret. Next, the formed fibres are cooled and/or washed and, optionally, drawn to produce fibres or a yarn having properties which render said fibres pre-eminently suitable for textile or technical application.
Examples of different spinning processes are to be found, e.g., in Fundamentals of Fibre Formation (The science of Fibre Spinning and Drawing), A. Ziabicki, Wiley lnterscience Publication, London, 1976, or in Synthesefasern (Grundlagen, Technologie, Verarbeitung und Anwendung), B. von Falkai, Verlag Chemie, Weinheim, 1981.
On conclusion of the spinning process the formed fibres are wound or collected in some other way, and the mechanical properties and structural parameters of the fibres are measured.
The measuring of the properties of the fibres takes place under carefully controlled temperature and atmospheric humidity conditions, according to fixed procedures, this in order to enable comparison of the results of different measurements. Generally, such measurements are carried out in a laboratory specially equipped for the purpose. In consequence, it is impossible to make use of the result of these measurements during the actual spinning process, e.g., to select fibres having particular properties, such as a certain breaking tenacity, elongation at break or level of shrinkage, or for their suitability for dye uptake.
A well-known, long-used method of determining the dye uptake of textile fibres is to employ a comparative test in which various fibre samples have their different uptakes of a standard dye determined. To this end small pieces of yarn of different samples are knitted into hose. Next, the hose is dyed with a dye critical to the material under critical conditions, i.e., the time during which the knitted hose is contacted with the liquid in which the dye is dissolved is too short to effect full saturation of the hose with dye or complete uptake of the dye from the bath. In addition, such a test employs dyes which have a slow uptake by the fibrous material in question, and the determination is carried out at a comparatively low temperature. The dye uptake is then evaluated visually by indicating whether a yam sample""s dye uptake is superior, inferior or normal as compared with that of an adjoining yarn sample.
Major drawbacks of this known method are that:
the results obtained are relative
the determination is dependent on the person carrying out the test
the method is complex and time-labour-intensive
only comparatively large differences in dye uptake can be made visible.
Admittedly, it is possible to remove the subjective elements present in this determination by using photometric equipment (e.g., a HunterLab spectrometer), but in that case the knitted structure of the hose is found to have a major effect on the determination.